Stale DNF metadata after system clock rollback

Stale DNF metadata after system clock rollback

The goal is to understand how DNF decides whether its cached repository metadata remains valid when the system clock is set backward, potentially bypassing the metadata_expire timer.

Constraints include differences in cache layout and expiration logic between DNF releases prior to version 4.0 and later versions, the absence of an automatic mechanism to detect clock adjustments, and the possibility that simultaneous metadata refreshes from multiple processes could produce partial or corrupted cache files.

• Does DNF treat metadata as stale immediately after a backward clock change, or does it rely solely on the metadata_expire timer?
• How does DNF coordinate concurrent metadata refreshes to avoid creating incomplete or corrupted cache files?
• Are there any version‑specific safeguards that mitigate the risk of using stale metadata under these conditions?